The invention is in the field of medical devices for intraocular sample delivery and withdrawal. More particularly, it pertains to instruments shaped and dimensioned for insertion into the orbit along an insertion path which extends along the periphery of the eye in a posterior direction to place the instrument tip adjacent posterior portions of the eye such as the sclera, choroid, the retina, or vitreous chamber.
Throughout this application various publications and patents are referenced and citations are provided in parentheses for them. The disclosures of these publications in their entireties are hereby incorporated by reference into this application to describe more fully the state of the art to which this invention pertains.
The remarkable efficiency of the eye as an organ for vision results from its highly specialized organization and the complicated coordination of its component parts which are vital to the process of normal vision. Damage to any essential structure can result in impairment of vision. Accordingly, it is particularly important that instruments designed for use in or around the eye (ocular globe) to aid in treatment or diagnosis of visual impairment must be safe and reliable, while at the same time permitting access to regions of the eye that are not easily accessible.
A common feature of known prior art intraocular transplantation instruments is that they carry out sample delivery by penetrating an anterior part of the eye, i.e. via a transcorneal or transcleral route, which creates the risks of corneal ulceration, cataract formation, and other anterior penetration problems. One exemplary prior art instrument is a microspatula which administers cells to the eye through a trans-scleral or trans-corneal surgical incision (12). Another exemplary prior art instrument is a glass micropipet which replaces cells in the retina by entering the eye anteriorly through an incision via the scleral route (10). Yet another exemplary instrument is a glass micro canula which effects transplantation of cells into the retina by entering the eye anteriorly through a surgical incision via a trans-scleral or trans-corneal route.
Known prior art instruments do not directly effect entry into the eye. Instead, an entry portal, i.e. a surgical incision, is believed to be necessary. Surgery involves inherent risks and possible complications such as vitreous loss, cataract formation, and intraocular infection. Of course, any instrument which requires surgical procedures before it could be used is less desirable than instruments which do not. Further, because such prior art instruments effect entry through surgical incisions, any attempts to implant at multiple sites within the eye can be exceedingly difficult and dangerous.
In contrast, the subject invention provides instruments which can enter the eye directly, without requiring a surgical incision as a prerequisite. Importantly, the subject invention makes it possible to transplant at multiple sites within the eye without the undesirable risks and consequences of multiple surgical procedures.
Further, in contrast to the prior art instruments, the subject invention provides a particularly effective way to control the depth of intraocular penetration. One embodiment of the invention uses a uniquely shaped and positioned adjustable collar to regulate the depth to which the instrument tip may enter the intraocular area. In contrast, it is believed that known prior art instruments cannot be pre-set to penetrate only to a pre-determined desired depth; instead, the penetration depth into the intraocular area is determined at the time of penetration. These instruments do not have the advantage of effecting intraocular penetration at a predetermined depth. This feature is believed to be particularly important because the ability to limit the actual penetration depth of an intraocular instrument could alleviate or eliminate important disorders or symptoms that can be associated with intrusion into the intraocular area. Another important benefit is the invention's ability to have a pre-set or predetermined depth of penetration into the eye, is that sample delivery or withdrawal can be pinpointed at the desired part of the eye, e.g. only the scleral area, the choroid area, the sub-retinal area the retinal area, or the vitreous area, etc.
The known prior art instruments typically provide sample delivery but not sample withdrawal with the same instrument. Further, it is believed that the known prior art instrument cannot be effectively pre-set to dispense only a desired volume but rather dispense the sample according to the pressure exerted by, or movement of, the operator at the time of sample delivery, i.e. sample size is not predetermined and dispensed before the instrument is in the eye. Accordingly, prior to the procedure of eye penetration, there is an effective way to be sure that only a predetermined amount of sample will in fact be administered to or withdrawn from the intraocular area.
The invention is believed to provide a new and reliably reproducible means for retinal transplantation without a surgical procedure on the eye as a prerequisite. In contrast, the known literature proposes techniques for intraretinal transplantation which require surgically opening the eye. Lopez, et al. (10) discuss a technique which required making a pars plana incision and inserting a micropipette through the globe into the subretinal space.
The method described by Lopez involves forming a retinal detachment in order to properly place the transplant. They note that "there are a number of potential pitfalls associated with this technique" and remark that the host epithelium must first be detached. This is a procedure which in the case of the human eye can be associated with subretinal neovascularization. In addition they note that "it may be difficult to be certain that no cells enter the vitreous cavity."
The technique proposed by Sheedlo et al. (11) requires excision of the superior rectus muscle, followed by an incision into the globe with a blade which penetrates the sclera and choroid to expose the subretinal space, prior to performing the transplantation of cells into this locus. Following the injection of material, the incision must be closed surgically with suture material.
Silverman and Hughes (12) report a technique which also involves a preliminary ocular incision prior to implantation of tissue. They propose a trans-corneal approach to the subretinal space which involves making a transverse incision through the cornea and then traversing the entire globe in order to reach the posterior pole.